Not quite sure what you're trying to accomplish here. Do you just want to measure the sound level or do you want to record it?
If you just want to measure the sound level, head down to Radio Shack and buy a Sound Pressure Level (SPL) meter. You can pick one up for under $50, and it's useful to have around for all sorts of different things!
I don't think you want to try to record it, especially from that distance. The ambient noise you're going to pick up is going to skew your SPL readings anyway.
And to answer your last question, yes, you are correct. According to theory, no higher than 0dB for digital, while analog can jump above 0dB occasionally (but you should still stick as close to 0dB as possible). I say in theory because in reality, you've got about 6dB of headroom in the digital domain. I've been able to record tracks in my home studio with the meters nearly pegged at 0dB with no clipping whatsoever. Of course, that doesn't give the mastering people much room to work with....